diff --git a/codearchiver/core.py b/codearchiver/core.py
index 41f8c8e..0e4a58c 100644
--- a/codearchiver/core.py
+++ b/codearchiver/core.py
@@ -140,7 +140,7 @@ class Metadata(list[tuple[str, str]]):
 
 		repeatableKeys = set(field.key for field in self._allFields if field.repeatable)
 		repeatedKeys = set(key for key, count in keyCounts.items() if count > 1)
-		repeatedUnrepeatableKeys = repeatedKeys - repeatableKeys
+		repeatedUnrepeatableKeys = repeatedKeys - repeatableKeys - unrecognisedKeys
 
 		errors = []
 		if unrecognisedKeys: